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JPH04246999

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DESCRIPTION JPH04246999
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
narrow directional microphone, and more particularly to reduction of wind noise in a narrow
directional microphone in which an acoustic tube is fitted to a microphone unit.
[0002]
2. Description of the Related Art Various types of narrow directional microphones, called line
microphones or the like in which the directivity is narrowed by fitting one end of an acoustic
tube to the tip of a microphone unit, have been provided conventionally. An example of a
conventional narrow directional microphone will be described with reference to FIG. 6. The
narrow directional microphone 1 has a microphone unit 4 having a front acoustic terminal 2 and
a rear acoustic terminal 3 and openings 5 for a plurality of acoustic resistances on its peripheral
surface. And the acoustic pipe 6 in which One end of the acoustic tube 6 is fitted to the front
acoustic terminal 2 side of the microphone unit 4, and the rear acoustic terminal 3 side of the
microphone unit 4 is positioned in a free sound field. On the outer peripheral surface of the
acoustic tube 6, an acoustic resistance material 7 made of non-woven fabric such as felt or nylon
mesh is provided. An outer tube 9 having an inner diameter larger than the outer diameter of the
acoustic resistance material 7 and having a plurality of through holes 8 formed therein is fitted
to the outer peripheral surfaces of the microphone unit 4 and the acoustic tube 6. The
microphone unit 4 is supported in the outer tube 9 by a fixing ring 10.
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[0003]
On the other hand, in the microphone, a pressure difference is generated by wind before and
after the diaphragm of the microphone unit, and this pressure difference becomes wind noise.
The wind noise increases in the order of the nondirectional microphone, the unidirectional
microphone, and the narrow directional microphone as described above. The wind noise of the
narrow directional microphone is large because one end of the acoustic tube 6 is directly and
completely connected to the front acoustic terminal 2 of the microphone unit 4. The tip 11 of the
front end becomes the sound inlet of the front acoustic terminal 2, the distance to the rear
acoustic terminal 3 becomes long, a very large pressure difference occurs, and as a result, a large
wind noise is generated in the bass region .
[0004]
In order to improve such a defect, for example, in Japanese Patent Application Laid-Open No. 62118698, the outer peripheral surface of the microphone unit is spaced from the inner peripheral
surface of the acoustic pipe in the rear end of the acoustic pipe. It has been proposed to position
and form a passage between the front and rear acoustic terminals to reduce the pressure
differential due to wind. With this structure, even if there is a pressure difference between the
front acoustic terminal and the rear acoustic terminal, the air on the high pressure side can be
made to flow to the low pressure side, thereby reducing the pressure difference and reducing
wind noise. be able to.
[0005]
However, locating the microphone unit with a gap in the acoustic tube is suitable for the case
where the outer diameter of the microphone is large, since the acoustic tube also becomes large
accordingly. However, if it is desired to make the outer diameter of the microphone extremely
thin, for example, 8 mm in diameter, it is necessary to use a very small microphone unit of a
much smaller diameter. The smaller the microphone unit is, the more the performance thereof
deteriorates, and it becomes extremely difficult to obtain the desired performance.
[0006]
Therefore, an object of the present invention is to provide a narrow directional microphone with
reduced wind noise by reducing the pressure difference between the front and rear acoustic
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terminals without increasing the outer diameter.
[0007]
SUMMARY OF THE INVENTION In the narrow directional microphone of the present invention,
the microphone unit is connected to one end of the acoustic tube, and the inner peripheral
surface thereof has a ring-shaped projection projecting in the center direction A unit case, a
diaphragm ring which is inserted into the unit case and which supports the diaphragm on one
axial end surface thereof, and an insulating seat which abuts on one end surface of the
diaphragm ring in the unit case and accommodates a back electrode plate or the like; It has a
diaphragm ring and a lock ring that fixes the insulating seat so as to press it against the
protrusion of the unit case, and an air leak path is formed in the unit case from the front acoustic
terminal to the rear acoustic terminal. It is characterized by being done.
[0008]
[Operation] Since an air leakage passage is formed between the front acoustic terminal and the
rear acoustic terminal in the unit case, even if there is a pressure difference between the front
acoustic terminal and the rear acoustic terminal, Since the high pressure side air can flow into
the low pressure side, the pressure difference is reduced and wind noise can be reduced.
Furthermore, since the leak path is formed in the unit case, a microphone unit having a diameter
approximately equal to the outside diameter can be used when obtaining a microphone with a
desired outside diameter.
[0009]
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with
reference to an embodiment shown in the drawings. As in the prior art, a plurality of openings 21
for acoustic resistance are formed on the peripheral surface thereof and made of metal such as
aluminum. The rear end of the acoustic tube 22 is fitted with one end of a unit case 23
accommodating a substantially cylindrical microphone unit whose inner circumferential surface
is in close contact with the outer circumferential surface of the acoustic tube 22.
The unit case 23 is made of metal such as aluminum similarly to the acoustic tube 22, and the
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other end side is provided with a plurality of openings 24 serving as rear acoustic terminals at
predetermined intervals in the circumferential direction. The other end of the unit case 23 is
similarly fitted with one end of a grip case 25 having a cylindrical shape.
[0010]
A projection 26 projecting in the center direction is integrally formed on the inner peripheral
surface of the unit case 23 at a substantially central portion of the axial length, and an opening
27 is formed in the central portion. There is. The inner peripheral surface of the unit case 23 on
the other surface side of the protrusion 26 in contact with the rear end of the acoustic tube 22
on one surface of the protrusion 26 has a diameter greater than the inner peripheral surface on
the acoustic tube 22 side. In other words, the other side of the projection 26 has a diameter of
about 0.1 mm, and a metal mesh 28 of about 100 mm mesh is used to connect the diaphragm
ring 29 in the axial direction. The end face is in contact. The outer diameter of the diaphragm
ring 29 is smaller than that of the inner peripheral surface of the unit case 23. An insulating seat
32 is attached to the other axial end surface of the diaphragm ring 29 via the diaphragm 31. The
insulating seat 32 is a so-called casing having a back electrode plate and a back electrode
chamber (both not shown) inside as in the prior art. The outer peripheral surface of the
insulating seat 32 is configured to have the same size as the outer diameter of the diaphragm
ring 29.
[0011]
A lock ring 33 made of metal such as aluminum is located at the end of the insulating seat 32
opposite to the diaphragm ring 29. As shown in detail in FIGS. 3A and 3B, the lock ring 33 has a
screw 34 cut on its outer peripheral surface, and this screw is a screw 35 formed on the inner
peripheral surface of the unit case 23 (FIG. ) And screwed in the desired position. A groove 36
passing from the outer peripheral surface to the inner peripheral surface is formed at an interval
of approximately 180 degrees on one axial end surface of the lock ring 33, and one end is an axis
of the lock ring 33 substantially at the center of the groove 36. The other end of the
communication hole 37 opened to the other end surface in the direction is opened. The lock ring
33 presses and fixes the diaphragm ring 29 and the insulating seat 32 to the side of the
projection 26. When fixed, there is a gap 38 for an air passage between the outer peripheral
surface thereof and the inner peripheral surface of the unit case 23. The diaphragm ring 29 and
the insulating seat 32 are arranged as formed.
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[0012]
In the middle and higher frequency bands, the metal mesh 28 becomes the front acoustic
terminal, but in the low frequency band, the tip of the acoustic tube 22 becomes the front
acoustic terminal as in the prior art, and the rear acoustic terminal The distance between the unit
case 23 and the opening 24 is long, and a very large pressure difference occurs between the two.
However, as described above, an air passage is formed by the gap 38 between the outer
peripheral surface of the diaphragm ring 29 and the insulating seat 32 and the inner peripheral
surface of the unit case 23 from the air gap of the metal mesh 28 itself. Since the groove 36 and
the communication hole 37 communicating with the air passage are formed, the gap 38, the
groove 36 and the communication hole 37 become a leak path of air, and the pressure between
the front acoustic terminal and the rear acoustic terminal Even if there is a difference, the air on
the high pressure side can flow into the low pressure side, so the pressure difference becomes
smaller and wind noise can be reduced. Furthermore, the air leakage passage is formed between
the front surface of the diaphragm ring 29 and the outer peripheral surfaces of the diaphragm
ring 29 and the insulating seat 32 and the inner peripheral surface of the unit case 23, and has
no factor that increases the appearance. Therefore, since the unit case 23 having an outer
diameter approximately equal to the outer diameter of the acoustic tube can be used, the
performance of the microphone is not degraded. Furthermore, since the conventional ones can
be used as they are, except for the unit case 23, the metal mesh 28 and the lock ring 33, they can
be provided inexpensively.
[0013]
FIG. 4 shows the wind noise characteristics of the conventional narrow directional microphone
shown in FIG. 6, and FIG. 5 shows the wind noise characteristics of the narrow directional
microphone of the embodiment described above. It was found that the wind noise of the
embodiment was low. It was also found from this measurement that it is particularly effective in
the frequency band below 200 Hz.
[0014]
A metal mesh 28 is interposed between the projection 26 and the diaphragm ring 29 to form a
gap 38. However, the communication hole similar to the communication hole 37 of the lock ring
33 is this diaphragm ring 29 may be provided to form a leak path. Furthermore, in the abovedescribed embodiment, as in the prior art, the outer periphery of the acoustic tube 22 and the
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unit case 23 may of course be covered with an outer tube.
[0015]
As described above, in the narrow directional microphone according to the present invention, the
microphone unit is connected to one end of the acoustic tube, and the inner circumferential
surface thereof has a ring-shaped projection projecting in the center direction A unit case, a
diaphragm ring which is inserted into the unit case and which supports the diaphragm on one
axial end surface thereof, and an insulating seat which abuts on one end surface of the
diaphragm ring in the unit case and accommodates a back electrode plate or the like; A
diaphragm ring and a lock ring for fixing the insulating seat so as to press it against the
projection of the unit case, and in the unit case there is an air leak path between the front
acoustic terminal and the rear acoustic terminal. Because it is formed, air on the high pressure
side flows into the low pressure side even if there is a pressure difference between the front and
rear sound terminals. Since bets can, the pressure difference is small, it is possible to reduce the
wind noise. Furthermore, since this leak path is formed in the unit case, it is possible to use a unit
having an outer diameter approximately equal to the outer diameter of the acoustic tube, so that
the performance of the microphone is not degraded.
[0016]
Brief description of the drawings
[0017]
1 is a plan view schematically showing an embodiment of the present invention.
[0018]
2 is a longitudinal sectional view showing a portion surrounded by an alternate long and short
dash line in FIG.
[0019]
3 is a view showing only the lock ring of FIG. 2, (A) is a plan view thereof, (B) is a longitudinal
sectional view thereof.
[0020]
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4 is a graph showing wind noise characteristics in this embodiment.
[0021]
5 is a graph showing the wind noise characteristics of the conventional narrow directional
microphone.
[0022]
6 is a longitudinal sectional view schematically showing an example of a conventional narrow
directional microphone.
[0023]
Explanation of sign
[0024]
21, 24, 27 Openings 22 Sound tube 23 Unit case 26 Protrusions 28 Metal mesh 29 Diaphragm
ring 31 Diaphragm 32 Insulating seat 33 Locking ring 36 Groove 37 Communication hole 38
Gap
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